基于ROS/HIF-1通路探讨白花蛇舌草多糖对鼻咽癌裸小鼠肿瘤的抑制作用及机制

目的:基于活性氧（ROS）/缺氧诱导因子-1（HIF-1）通路探讨白花蛇舌草多糖对鼻咽癌裸小鼠肿瘤的抑制作用及其可能作用机制。方法:56只BALB/c裸小鼠于右侧腋下接种CNE-2细胞悬液诱导鼻咽癌成瘤,成瘤后的裸小鼠随机分为:模型组、顺铂组（DDP,5 mg/kg）、白花蛇舌草多糖低剂量组（50 mg/kg）、白花蛇舌草多糖中剂量组（100 mg/kg）、白花蛇舌草多糖高剂量组（200 mg/kg）、阴性对照组（NC-siRNA）、si-HIF-1α组、si-HIF-1α+白花蛇舌草多糖组,每组6只,剩余6只裸小鼠作为空白组。各组按相应剂量分别腹腔注射给药,连续14天。测定裸小鼠瘤重及肿瘤体积［苏木素-伊红（HE）染色观察肿瘤组织病理学变化［流式细胞术检测肿瘤组织Treg细胞数量［免疫组化染色检测肿瘤组织Foxp3表达［荧光TUNEL染色检测肿瘤组织细胞凋亡［酶联免疫吸附测定法（ELISA）检测肿瘤组织中ROS含量［实时荧光定量聚合酶链式反应（real-time PCR）和蛋白免疫印迹法（Western blot）分别检测肿瘤组织HIF-1α、GLUT1、HK2 mRNA及蛋白表达。结果:与模型组比较,白花蛇舌草多糖高剂量组可明显降低肿瘤重量,降低Foxp3、HIF-1α、GLUT1、HK2表达,明显缩小瘤体积,降低Treg细胞数量,明显增加细胞凋亡及ROS含量（P＜0.01）。与si-HIF-1α组比较,si-HIF-1α+白花蛇舌草多糖组HIF-1α、GLUT1、HK2表达明显降低（P＜0.05）。与模型组比较,si-HIF-1α+白花蛇舌草多糖组ROS含量明显升高,瘤重及肿瘤体积明显减小（P＜0.05）。结论:白花蛇舌草多糖对鼻咽癌裸小鼠肿瘤具有抑制作用,其作用机制可能与降低HIF-1α、GLUT1、HK2表达有关。     

多氯联苯126与苯并(a)芘联合作用致代谢酶改变对HepG2细胞遗传毒性的影响

背景与目的:探讨多氯联苯126(PCB126)对苯并(a)芘[B(a)P]遗传毒性的影响.材料与方法:设PCB126三个剂量(0.01、0.10、1.00 nmol/L),B(a)P一个剂量(50 μmol/L)组,设三甲基胆蒽(3-MC)为阳性对照,二甲基亚砜(DMSO)为溶剂对照,以各PCB126浓度染毒HepG2细胞48 h后,再与B(a)P联合染毒24h.通过荧光分光光度法测定各组细胞CYP1A1酶活性(EROD);并采用胞质分裂阻滞法微核实验(CBMNT)分析各组细胞的微核率(MN%o),并计算核分裂指数(NDI).结果:与溶剂对照相比,PCB126各浓度组和50 μmol/L的B(a)P单独作用及联合作用均可诱导CYP1A1酶活性显著增加,其差异均具有统计学意义(P＜0.05,P＜0.01).微核率显著升高仅见于50 μmol/L的B(a)P单独作用组,与溶剂对照组相比差异有统计学意义(P＜0.01).0.10、1.00 nmol/L的PCB126和50 μmol/L的B(a)P联合作用时,与B(a)P单独作用相比,CYP1A1酶活性和微核率均显著升高,差异有统计学意义(P＜0.05,P＜0.01).结论:PCB126在本试验条件下未显示出遗传毒性作用,但对B(a)P的遗传毒性作用具有一定的增强效应.     

白花蛇舌草对U14宫颈癌抗肿瘤作用的实验研究

目的 探讨白花蛇舌草(HD)对U14宫颈癌细胞移植瘤的抑制作用及可能的分子生物学机制.方法 建立裸鼠U14宫颈癌模型,用不同剂量白花蛇舌草进行治疗,并以顺铂治疗组为阳性对照,通过HE染色观察肿瘤组织病理变化,流式细胞仪检测肿瘤细胞凋亡情况,采用PCR-TRAR-ELISA方法定量检测细胞端粒酶活性水平.结果 HD对U14宫颈癌细胞移植瘤生长有明显抑制作用,并可诱导U14细胞凋亡,经中、高剂量的HD治疗后U14细胞端粒酶活性明显下降,与阴性对照组比较差异显著(P＜0.01),与阳性对照组比较无明显差异(p＞0.05).结论 一定剂量HD具有诱导U14宫颈癌细胞凋亡和抑制肿瘤细胞端粒酶活性的作用,这可能是其抑制肿瘤生长的重要分子生物学机制.     

Evaluation of genetic toxicity of bryostatin

目的:检测草苔虫内酯的遗传毒性.方法:采用Ames试验、体外培养中国仓鼠卵巢(chinese hamster ovary,CHO)细胞染色体畸变试验和小鼠骨髓微核试验检测草苔虫内酯的遗传毒性.结果:Ames试验显示在每皿100、10、1、0.1g受试剂量下,在加或不加S9代谢活化系统时对组氨酸缺陷型鼠伤寒沙门氏菌TA97、TA98、TA100、TA102及TA1535所诱发的回复突变菌落数均与溶剂对照的突变菌落数相近.体外培养CHO细胞染色体畸变试验结果显示,在3.75、1.88和0.94 g/ml 3个剂量组,在加S9条件下培养24 h和不加S9培养24、48 h的CHO细胞染色体畸变率与溶剂对照组相比差异有统计学意义(P＜0.05).小鼠骨髓微核试验,在12.5、25、50 g/kg 3个剂量下对ICR小鼠的微核诱发率呈剂量反应关系,与溶剂对照组相比差异有统计学意义(P＜0.01).结论:在本实验条件下,草苔虫内酯对鼠伤寒沙门氏菌无致突变性,对哺乳动物培养细胞染色体的致畸变作用为可疑阳性,对ICR小鼠有诱发骨髓嗜多染红细胞微核的效应,提示草苔虫内酯对人体具有潜在的遗传毒性.     

茶水提取物和茶多酚抑制诱变的类型及其机制

目的 :研究茶水提取物和茶多酚的去突变特征和机制 ,鉴别茶和茶多酚去突变的量效关系和抑菌关系 ,了解去突变剂与直接诱变剂(1_NP)、间接(Trp_P_1)诱变剂的抗突变作用方式和抑制效果。 方法 :用细胞外抑制诱变试验和改进型两次活化的Ames试验方法。 结果 :茶水提取物和与其相关的儿茶素等都存在非抑菌性的去突变效果 ,其中表没食子儿茶素没食子酸酯(EGCG)和茶黄素(TF)的效果最好。抗突变试验结果表明 ,茶水提取物对Trp_P_1( +S9)有显著的抗突变性 ,与Trp_P_1的混合液在非代谢活性条件时无诱变性 ;茶水提取物对1_NP( -S9)也有抑制活性 ,但比对Trp_P_1的抑制活性低(P<0.01) ,与1_NP混合物经代谢活化后有诱变性 ,且与非代谢活化的抗突变结果呈较高的相关性(r= -0.9694)。 结论 :茶多酚能抑制间接诱变剂的前体形成 ,也有对直接诱变剂构成阻断剂的作用 ,但是在阻断具有强氧化性的诱变剂时可能形成不稳定的结合物或不安全的结构物。     

B[a]P和DDT亚急性联合暴露对小鼠肝功能酶ALT、AST和γ-GT的影响及作用形式

目的:探讨不同剂量的苯并[a]芘(B[a]P)和滴滴涕(DDT)联合暴露对小鼠血清中谷丙转氨酶(ALT)、谷草转氨酶(AST)和γ-谷胺酰转移酶((λ)-GD的影响及作用形式.方法:成年雄性昆明种小鼠50只,随机分为10组即空白对照组(正常饲养)、溶剂对照组(食用油和二甲基亚砜处理)、低和高浓度B[a]P染毒组[1.0和10 mg/(kg·d)]、低和高浓度DDT染毒组[0.6和6 mg/(kg·d)]、低浓度DDT+低浓度B[a]P染毒组、低浓度DDT+高浓度B[a]P染毒组、高浓度DDT+低浓度B[a]P染毒组、高浓度DDT+高浓度B[a]P染毒组.染毒组各受试物经腹腔注射染毒,每日注射1次,连续31d.末次染毒24 h后通过眼球摘除取血,自动生化仪检测血清中ALT、AST、γ-GT的活性;并制作肝脏HE切片,观察肝细胞形态.采用两因素三水平析因设计的方差分析对数据进行统计分析.结果:与对照组比较,B[a]P和DDT单独染毒时,均能诱导ALT和AST活性升高(F=41.308,P=0.000;F=20.083,P=0.000),随各自染毒剂量的增加,ALT和AST活性升高,但二者联合暴露对AL和AST活性均不存在交互作用(分别为P=0.258,P=0.264).B[a]P和DDT单独染毒对γ-GT活性均未产生明显影响,联合暴露也不存在交互作用(P=0.816).HE染色观察到肝细胞膜界限模糊,发生水样变性,肝细胞中出现小空泡,呈蜂窝状,随染毒剂量增加,肝细胞质水样变性加剧,部分肝细胞质溶解,并且细胞核肿大,形状不规则.结论:在本实验条件下,B[a]P和DDT单独染毒均能诱导小鼠血清ALT和AST活性升高,不同剂量的B[a]P和DDT联合暴露对小鼠血清ALT、AST活性的作用形式主要表现为单独作用,而非交互作用.B[a]P和DDT的单独和联合暴露均未观察到对γ-GT的活性产生明显影响.     

煤尘颗粒及其与苯并(a)芘混合物的致突变性研究

背景与目的:探讨煤尘颗粒的致突变作用.材料与方法:采用Ames试验和姐妹染色单体交换(SCE)试验检测烟煤、无烟煤、褐煤粉尘颗粒及其与苯并(a)芘混合物的混悬液的致突变性.Ames试验采用TA97、TA98、TA100和TA102菌株,将3种煤尘颗粒及其与苯并(a)芘混合物各分为5000、500、50和5μg/皿4个剂量组,并分为加与不加S9两部分,细菌37℃培养48 h后计算回变菌落数;SCE试验采用健康成人外周血淋巴细胞,煤尘颗粒及其与苯并(a)芘混合物样品分为500、50和5μg/皿3个剂量组,标本37℃培养72h后制成染色体并计数染色单体交换频率(SCEs).2个试验均设阴性和阳性对照组,各剂量组均设3个平行样.结果:3种煤尘在加与不加S9时,其菌落数均不超过自发回变菌落数(SRM)的2倍,各剂量组之间无剂量效应关系,煤尘一苯并(a)芘混合物的菌落数与苯并(a)芘的菌落数相比,差异无统计学意义(P＞0.05),而且3种煤尘颗粒及其苯并(a)芘混合物组与对照组相比,均不能使SCEs显著升高(P＞0.05).结论:在本实验条件下,3种煤尘及其苯并(a)芘混合物均无致突变作用.     

茶多酚对小鼠Lewis肺癌移植瘤中NF-κB、COX-2、Survivin表达的影响

背景与目的 肺癌是全球第一大恶性肿瘤,前期研究表明茶多酚具有一定的抗肺癌新生血管生成作用,本研究旨在观察茶多酚对小鼠Lewis肺癌移植瘤中NF-κB、COX-2、Survivin表达的影响,进而探讨茶多酚抗新生血管生成的效应机制.方法 建立C57BL/6小鼠肺癌移植瘤模型,测定模型对照组、沙利度胺组、茶多酚组以及茶多酚联合沙利度胺组的肿瘤抑制率,并且采用免疫组化法检测各组NF-κB、COX-2、Survivin表达水平,以探讨其抗肿瘤的分子机制.结果 实验表明,茶多酚具有如下作用:①沙利度胺组、茶多酚组以及茶多酚联合沙利度胺组的肿瘤抑制率分别为17.26％、20.81％和44.32％,茶多酚联合沙利度胺组与模型组瘤重比较,差异具有统计学意义(P＜0.05)；②NF-κB表达在茶多酚组及联合用药组有所降低,与模型对照组相比.联合用药组NF-κB表达明显下降,差异具有统计学意义( P＜0.05)；③COX-2表达在各治疗组均有所下降,与模型对照组相比,联合用药组表达明显下降(P＜0.05)；④Survivin表达在各治疗组均较模型对照组明显降低(p＜0.05),其中茶多酚组下降最为明显(P＜0.01).结论 茶多酚联合沙利度胺组对肺癌有明显抑制作用,其机制可能与抑制NF-κB信号通路的异常激活、抑制NF-κB活化、降低COX-2表达、并降低内皮细胞Survivin表达从而抗肺癌新生血管生成相关.     

吸入异维甲酸用于预防肺癌的疗效观察

目的探讨吸入异维甲酸能够针对靶细胞发挥足够药效的方法,同时避免全身性中毒.方法给白鼠腹腔注射一次性剂量的氨基钾酸脂或二苯骈(a)芘(BaP)或特异亚硝胺类化合物4-甲基亚硝胺-1(3-吡啶基)-1-丁酮(NNK).从第2天开始,将白鼠分别置于浓度为1.3,20.7,481 mg/L的异维甲酸气雾剂中45 min.置于低浓度异维甲酸中的白鼠每日1次,中等浓度的异维甲酸剂量1周3次,置于高浓度异维甲酸中的白鼠1周2次.结果测到的总沉积剂量分别为0.24,1.6,24.9 mg/kg,据估算,其中16%沉积在肺部.肺部药物剂量的每周沉积量的计算结果分别为以前给接受过氨基钾酸脂的白鼠进行治疗而未能发生作用的口服剂量的0.01%,0.07%和1.1%.10～16周以后,解剖白鼠,统计肺部增生和肿瘤的数量.对于所有的致癌物质,接受高剂量异维甲酸的白鼠,肿瘤的多样性出现了56%～80%(P＜0.005)的降低;接受中等剂量异维甲酸的白鼠,肿瘤的多样性出现了67%～88%(P＜0.005)的降低;接受小剂量治疗的经过BaP和NNK处理的白鼠,多样化的降低程度分别为30%(P＜0.13)和16% (P＜0.30),差异无显著性.在接受BaP和NNK的白鼠中,增生区域的数量与剂量呈正相关,而与肿瘤数量成反比,表明有抑制作用.相对于接受乙醇吸入的白鼠,吸入中等剂量异维甲酸可以引起肺组织的维甲酸受体(RAR)的变化,具体表现为RARα(3.9倍于乙醇组)、RARβ(3.3倍)和RARγ(3.7倍).结论维甲酸受体是该系统内的类维生素A活性的有效生物标志,吸入异维甲酸有利于有肺癌高发危险的人群预防肺癌.     

不同转移潜能鼻咽癌细胞钙电流特征与细胞迁徙能力的相关性

背景与目的:肿瘤转移活性与瘤细胞以迁徙运动潜能为代表的生物力学特性有关,而其迁移运动的生物力学机制又受制于细胞内的钙离子活动和钙电流特征.本文探讨不同转移潜能鼻咽癌单克隆亚系细胞钙电流特征,及与细胞迁徙运动潜能的相关性.方法:人鼻咽癌高转移潜能细胞株5-8F及低转移潜能细胞株6-10B分别与10%含药血清(由黄芪、党参、白花蛇舌草等组成)共同培养,MTT法检测含药血清对细胞增殖的影响,Western blot检测nm23-H1蛋白表达水平.利用全细胞膜片钳制方法观察细胞钙电流特征(药物作用20 min),划痕实验观察细胞迁移能力(药物作用24 h),比较分析其相关性.结果:6-10B细胞的nm23-H1表达水平(2.9±0.4)较5-8F细胞(2.3±0.21)高(P＜0.05).5-8F细胞内钙释放激活的钙电流ICRAC为(-1.39±0.36)nA,与6-10B细胞lCRAC[(-0.66±0.40)nA]相比差异有统计学意义(P＜0.05).通过划痕区的5-8F细胞数(350±3)也显著高于6-10B细胞(246±1)(P＜0.05).应用含药血清干预后,5-8F和6-10B细胞增殖活性差异无统计学意义(P＞0.05),5-8F细胞的nm23-H1表达水平(3.9±0.1)明显高于6-10B细胞(1.0±0.1)(P＜0.05).干预后,5-8F细胞ICRAC降至(-1.27±0.35)nA,平均抑制幅度为(1.90±0.47)%;6-10B细胞则降至(-0.37±0.23)nA,平均抑制幅度为(0.46±0.12)%,两者差异有统计学意义(P＜0.05),并出现与钙电流变化特点平行的细胞迁移能力变化,通过划痕线的5-8F细胞数明显减少(94±6),而6-10B细胞则受影响甚小(229±6,P＜0.05).干预前后5-8F细胞迁移能力变化具有显著性(P＜0.05),6-10B细胞则无显著性差异(P＞0.05).结论:不同转移潜能鼻咽癌细胞钙电流特征及细胞迁移能力以及nm23-H1表达存在明显差异.应用含药血清干预后,高转移潜能细胞5-8F出现了与细胞钙电流ICRAC降低幅度相平行的细胞迁移能力抑制,药物血清可增加5-8F细胞的nm23-H1活性.     

半枝莲、白花蛇舌草抗肿瘤的研究进展

体内外药理实验显示：半枝莲、白花蛇舌草抗肿瘤作用明显,而且二者在抗肿瘤方剂中常以药对形式出现。本文分析二者抗肿瘤的机制,并探讨二者抗肿瘤的协同作用,为组方及临床应用提供理论依据。     

Pharmacokinetics and safety of green tea polyphenols after multiple-dose administration of epigallocatechin gallate and polyphenon E in healthy individuals.

PURPOSE: Green tea and green tea polyphenols have been shown to possess cancer preventive activities in preclinical model systems. In preparation for future green tea intervention trials, we have conducted a clinical study to determine the safety and pharmacokinetics of green tea polyphenols after 4 weeks of daily p.o. administration of epigallocatechin gallate (EGCG) or Polyphenon E (a defined, decaffeinated green tea polyphenol mixture). In an exploratory fashion, we have also determined the effect of chronic green tea polyphenol administration on UV-induced erythema response. EXPERIMENTAL DESIGN: Healthy participants with Fitzpatric skin type II or III underwent a 2-week run-in period and were randomly assigned to receive one of the five treatments for 4 weeks: 800 mg EGCG once/day, 400 mg EGCG twice/day, 800 mg EGCG as Polyphenon E once/day, 400 mg EGCG as Polyphenon E twice/day, or a placebo once/day (8 subjects/group). Samples were collected and measurements performed before and after the 4-week treatment period for determination of safety, pharmacokinetics, and biological activity of green tea polyphenol treatment. RESULTS: Adverse events reported during the 4-week treatment period include excess gas, upset stomach, nausea, heartburn, stomach ache, abdominal pain, dizziness, headache, and muscle pain. All of the reported events were rated as mild events. For most events, the incidence reported in the polyphenol-treated groups was not more than that reported in the placebo group. No significant changes were observed in blood counts and blood chemistry profiles after repeated administration of green tea polyphenol products. There was a >60% increase in the area under the plasma EGCG concentration-time curve after 4 weeks of green tea polyphenol treatment at a dosing schedule of 800 mg once daily. No significant changes were observed in the pharmacokinetics of EGCG after repeated green tea polyphenol treatment at a regimen of 400 mg twice daily. The pharmacokinetics of the conjugated metabolites of epigallocatechin and epicatechin were not affected by repeated green tea polyphenol treatment. Four weeks of green tea polyphenol treatment at the selected dose and dosing schedule did not provide protection against UV-induced erythema. CONCLUSIONS: We conclude that it is safe for healthy individuals to take green tea polyphenol products in amounts equivalent to the EGCG content in 8-16 cups of green tea once a day or in divided doses twice a day for 4 weeks. There is a >60% increase in the systemic availability of free EGCG after chronic green tea polyphenol administration at a high daily bolus dose (800 mg EGCG or Polyphenon E once daily).     

Inhibition of N-nitrosodiethylamine- and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced tumorigenesis in A/J mice by green tea and black tea.

The effect of p.o. administration of tea on nitrosamine-induced carcinogenesis was investigated. Female A/J mice were given N-nitrosodiethylamine (NDEA) (10 mg/kg) p.o. once a week for 8 weeks and were killed 16 weeks after the last dose. More than 90% of the mice had forestomach and lung tumors. The animals had an average of 8.3 forestomach and 2.5 lung tumors/mouse. With 0.63 or 1.25% green tea infusion (12.5 g green tea leaves brewed with 1 liter of boiling water) as the sole source of drinking water for the entire experimental period, the pulmonary tumor incidence was decreased by 18 or 44%, and the tumor multiplicity was reduced by 36 or 60%, respectively. The treatments also decreased the forestomach tumor incidence by 18 or 26% and tumor multiplicity by 59 or 63%, respectively. Administration of 0.63 or 1.25% green tea infusion, either during the NDEA treatment period only or starting 1 week after the completion of NDEA treatment, also decreased the pulmonary tumor incidence and multiplicity and the forestomach tumor multiplicity. The inhibitory effects of green tea infusion were also observed in a similar experiment using a higher dosage of NDEA (20 mg/kg). Treatment of female A/J mice with a single dose (103 mg/kg) of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) resulted in the formation of pulmonary adenomas in almost all of the animals with an average of 9.3 tumors/mouse after 16 weeks. When 0.6% decaffeinated green tea or black tea extract was given during the NNK-treatment period, tumor multiplicity was reduced by 67 or 65%, respectively. When the tea extract was given after the NNK-treatment period until the end of the experiment, 0.6% green tea extract decreased the tumor incidence and multiplicity by 30 and 85%, respectively. In this protocol, 0.6% black tea extract reduced tumor multiplicity by about 63% but did not significantly affect the tumor incidence. The results clearly demonstrated an inhibitory action of green tea and black tea on nitrosamine-induced tumorigenesis.     

Inhibitory effect of topical application of a green tea polyphenol fraction on tumor initiation and promotion in mouse skin.

A green tea polyphenol fraction was evaluated for its ability to inhibit tumor initiation by polycyclic aromatic hydrocarbons and tumor promotion by a phorbol ester in the skin of CD-1 mice. Topical application of the green tea polyphenol fraction inhibited benzo[a]pyrene- and 7,12-dimethylbenz[a]-anthracene-induced tumor initiation as well as 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced tumor promotion. Topical application of the green tea polyphenol fraction also inhibited TPA-induced inflammation, ornithine decarboxylase activity, hyperplasia and hydrogen peroxide formation. Studies with individual polyphenolic compounds in green tea indicated that topical application of (-)-epigallocatechin gallate, (-)-epigallocatechin and (-)-epicatechin gallate inhibited TPA-induced inflammation in mouse epidermis.     

Modulation of human glutathione s-transferases by polyphenon e intervention.

PURPOSE: Green tea consumption has been associated with decreased risk of certain types of cancers in humans. Induction of detoxification enzymes has been suggested as one of the biochemical mechanisms responsible for the cancer-preventive effect of green tea. We conducted this clinical study to determine the effect of repeated green tea polyphenol administration on a major group of detoxification enzymes, glutathione S-transferases (GST). METHODS: A total of 42 healthy volunteers underwent a 4-week washout period by refraining from tea or tea-related products. At the end of the washout period, a fasting blood sample was collected, and plasma and lymphocytes were isolated for assessment of GST activity and level. Following the baseline evaluation, study participants underwent 4 weeks of green tea polyphenol intervention in the form of a standardized Polyphenon E preparation at a dose that contains 800 mg epigallocatechin gallate (EGCG) once a day. Polyphenon E was taken on an empty stomach to optimize the oral bioavailability of EGCG. Upon completion of the intervention, samples were collected for postintervention GST assessment. RESULTS: Four weeks of Polyphenon E intervention enhanced the GST activity in blood lymphocytes from 30.7 +/- 12.2 to 35.1 +/- 14.3 nmol/min/mg protein, P = 0.058. Analysis based on baseline activity showed that a statistically significant increase (80%, P = 0.004) in GST activity was observed in individuals with baseline activity in the lowest tertile, whereas a statistically significant decrease (20%, P = 0.02) in GST activity was observed in the highest tertile. In addition, Polyphenon E intervention significantly increased the GST-pi level in blood lymphocytes from 2,252.9 +/- 734.2 to 2,634.4 +/- 1,138.3 ng/mg protein, P = 0.035. Analysis based on baseline level showed that this increase was only significant (P = 0.003) in individuals with baseline level in the lowest tertile, with a mean increase of 80%. Repeated Polyphenon E administration had minimal effects on lymphocyte GST-mu and plasma GST-alpha levels. There was a small but statistically significant decrease (8%, P = 0.003) in plasma GST-alpha levels in the highest tertile. CONCLUSIONS: We conclude that 4 weeks of Polyphenon E administration resulted in differential effects on GST activity and level based on baseline enzyme activity/level, with GST activity and GST-pi level increased significantly in individuals with low baseline enzyme activity/level. This suggests that green tea polyphenol intervention may enhance the detoxification of carcinogens in individuals with low baseline detoxification capacity.     

Green tea catechin intervention of reactive oxygen species-mediated ERK pathway activation and chronically induced breast cell carcinogenesis

Long-term exposure to low doses of environmental carcinogens contributes to sporadic human breast cancers. Epidemiologic and experimental studies indicate that green tea catechins (GTCs) may intervene with breast cancer development. We have been developing a chronically induced breast cell carcinogenesis model wherein we repeatedly expose non-cancerous, human breast epithelial MCF10A cells to bioachievable picomolar concentrations of environmental carcinogens, such as 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and benzo[a]pyrene (B[a]P), to progressively induce cellular acquisition of cancer-associated properties, as measurable end points. The model is then used as a target to identify non-cytotoxic preventive agents effective in suppression of cellular carcinogenesis. Here, we demonstrate, for the first time, a two-step strategy that initially used end points that were transiently induced by short-term exposure to NNK and B[a]P as targets to detect GTCs capable of blocking the acquisition of cancer-associated properties and subsequently used end points constantly induced by long-term exposure to carcinogens as targets to verify GTCs capable of suppressing carcinogenesis. We detected that short-term exposure to NNK and B[a]P resulted in elevation of reactive oxygen species (ROS), leading to Raf-independent extracellular signal-regulated kinase (ERK) pathway activation and subsequent induction of cell proliferation and DNA damage. These GTCs, at non-cytotoxic levels, were able to suppress chronically induced cellular carcinogenesis by blocking carcinogen-induced ROS elevation, ERK activation, cell proliferation and DNA damage in each exposure cycle. Our model may help accelerate the identification of preventive agents to intervene in carcinogenesis induced by long-term exposure to environmental carcinogens, thereby safely and effectively reducing the health risk of sporadic breast cancer.     

Effects of different inducers of cytochrome P450 on the mutagenesis of the tobacco-specific nitrosamine 4-(methylnitrosamino)- 1-(3-pyridyl)-1-butanone (NNK) in Salmonella typhimurium TA1535.

The effects of six inducers of isoenzymes of cytochrome P450 on the mutagenicity of the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in Salmonella typhimurium strain TA1535 by hamster liver S9 and microsomes were investigated. Comparisons of the effects of dimethylsulfoxide (DMSO) as solvent for NNK were also made. The inducing agents were Aroclor 1254 (AROC), 3-methylcholanthrene (MC), phenobarbital (PB), dexamethasone (DXM), ethanol (ETOH) and isosafrol (ISF). The number of histidine-independent colonies induced by NNK in saline mediated by S9 from the inducing agents was as follows: ISF = AROC greater than PB greater than MC greater than DXM greater than ETOH. AROC-induced microsomes produced the most revertants by NNK (saline) greater than MC greater than PB = DXM and ISF greater than ETOH. The number of revertant colonies induced by NNK in DMSO was significantly less than that by NNK in saline for both hamster liver S9 and microsomes irrespective of the inducing agent. The greatest inhibitory effect of DMSO was observed with ISF-induced S9.     

Antimutagenic effects of polyphenolic compounds.

Smokers expose themselves to potent carcinogens daily. One of them is the nicotine-derived nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). Since estimates are that humans consume 1 g of phenolic compounds/day, we investigated the inhibitory effects of five structurally related polyphenolic compounds on the mutagenicity of NNK in Salmonella typhimurium TA1535. NNK at a concentration of 80 mM was activated by hamster liver microsomes. The antimutagenic efficacies were dose-related between the non-toxic concentrations of 0.1 and 0.5 mmol/dish in the following order: esculetin > ellagic acid > (+)-catechin > propyl gallate > (-)esculin. At the highest non-toxic dose tested (0.5 mmol/dish), these polyphenolics inhibited mutagenesis in TA1535 by 77%, 67%, 62%, 59% and 53%, respectively. The results of this study demonstrated that polyphenolic compounds may inhibit the activation of NNK.     

Mutagenesis induced by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and N-nitrosonornicotine in lacZ upper aerodigestive tissue and liver and inhibition by green tea

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and nitrosonornicotine (NNN) were administered to lacZ mice (MutaMouse) at equal concentrations in drinking water (2 weeks at 0.1 followed by 2 weeks at 0.2 mg/ml) over a 4 week period, for a total estimated dose of 615 mg/kg) and mutagenesis in a number of organs was measured. For mutagenesis induced by NNK the potency order was: liver > lung> pooled oral tissues kidney > esophagus > tongue. The mutant fraction varied from approximately 6 to 40 mutants per 10(-5) plaque forming units This corresponds to approximately 2-13 times the background levels. A somewhat different pattern was observed with NNN, where the order was liver > esophagus oral tissue approximately tongue > lung > kidney. The potency of NNK was about twice that of NNN in liver and lung, but somewhat less in aerodigestive tract tissue. When compared with results previously obtained for a similar administered dose of benzo[a]pyrene, NNK was approximately 10-100% as mutagenic in the corresponding organs. Reported target organs for carcinogenesis by NNN and NNK in rodents were targets for mutagenesis, but mutagenesis was also observed at other sites, suggesting that these sites are initiated. The effect of green tea consumption on mutagenesis by NNK was also investigated. Green tea reduced mutagenesis by approximately 15-50% in liver, lung, pooled oral tissue and esophagus.